KR20040073445A - Cooking vessel comprising a base made of a mulilayer meterial and a side wall, and article of mulilayer material - Google Patents

Abstract

The present invention relates to a cooking vessel comprising a bottom and a side wall made of a multilayer material, the multilayer material being continuously from the outside of the container to the inside of the container: having a thickness e _E , a Curie temperature of 30 to 350 ° C. and a 6.5 · 10 ^{− It} relates to a cooking vessel comprising an outer portion consisting of a ferromagnetic nickel-based alloy having a thermal expansion coefficient of ⁶ K ⁻¹ or more, and a core having a thickness e _c and comprising at least one layer selected from aluminum, aluminum alloy and copper. .

Description

Cooking vessel comprising a base made of a mulilayer meterial and a side wall, and article of mulilayer material

Cooking of food by induction is carried out by means of an inductor located under a glass-ceramic plate, generally permeable to electromagnetic fields, on a cooking vessel in which the contents to be heated are located. The flow of high-frequency current in the inductor generates a magnetic field that induces an eddy current in the vessel and is heated by the Joule effect.

There are also certain cooking utensils which are not equipped with glass-ceramic plates, the material which forms the subject of the patent permits the production of such containers.

To achieve high energy efficiency, the metal bases used in these containers have high electrical conductivity and high magnetic field amplification at the operating frequency used, 20-50 kHz. Therefore alloys that are ferromagnetic at the operating temperature of the vessel are generally used.

These containers have a smaller range because they must have a high corrosion resistivity on the side in contact with the food and also on their undersides must not deteriorate upon cleaning.

They must also be mechanically stable to keep the geometry of the vessel, in particular the flatness of the underside in contact with the top of the inductor. In fact, when the container is heated, the underside of the container is easy to expand. The side wall of the vessel, also called a skirt, raises the temperature to a lower temperature than the base and thus expands less, resulting in a radial compressive force on the base. The latter swells only with bowing, thereby reducing the energy efficiency of the assembly, resulting in user discomfort due to the noise and annoyances caused. This effect is reversible several times when the vessel is first used, but after several repeated thermal cycles due to the structural transformation of the underlying material. This phenomenon is particularly sensitive only if the bottom of the container contains a highly conductive material (eg aluminum or copper).

In the case of multi-layered materials, in general for various layers with very different coefficients of expansion, this difference in the coefficients can be attributed to the underside of the container, not only by induction heating but also by other heating methods (infrared, halogen, etc ...). And a tendency to attach various layers irreversibly degraded to localized debonding, resulting in a bimetallic strip effect resulting in a significant loss of container efficiency.

To make these containers, it is common practice to use ferritic stainless steel, such as austenitic stainless steel / ferritic stainless steel / austenitic stainless steel, for the ferromagnetic portion of 17% Cr-Fe or triple-layer symmetric materials. The disadvantage of these materials is that the Curie temperature exceeds 600 ° C, which can cause the underside of these containers to reach the Curie temperature, which can result in food loss or burning and deterioration of the container. This problem can occur even at temperatures below 600 ° C.

To remedy this problem, in FR 2 453 627 a method has been proposed for producing the bottom of a container from a triple-layer material comprising an alloy having a Curie point of 60 to 200 ° C. As long as the temperature of the vessel is below the Curie point, the alloy remains ferromagnetic and causes losses by induced currents to heat the vessel. As soon as the temperature of the vessel exceeds the Curie point, the alloy is no longer ferromagnetic and the heating stops, and heating is resumed only if the temperature of the vessel falls below the Curie point. Therefore, heat regulation of the container becomes possible. However, such materials are undesirable for cooking or frying foods because they need to reach temperatures in the range of 220-320 ° C. In addition, a method capable of ensuring good geometric stability of the container and good corrosion resistivity on both sides of the container has not been proposed in the patent.

The same principle was adopted in FR 2 689 748, which proposed a method for making a container from a triple-layer material comprising an alloy having a Curie point of 250 ° C., such as 64Fe-36Ni. However, this type of alloy has very common corrosion resistivity and very low coefficient of expansion. Yet this alloy is pressed against a metal layer with a significantly high coefficient of expansion and, when heated, results in deformation of the bottom of the container due to the bimetallic strip effect, which can sometimes be irreversible. Degradation can also be observed in the bonds between the layers, due to cyclic stress and creep phenomenon under temperature.

The present invention relates to a cooking vessel comprising a bottom and sidewalls made of a multilayer material, and more particularly to the multilayer material article, for the cooking of food by induction.

It is therefore an object of the present invention to include a multi-layered base which does not deform over time or during operation, each layer remains bound together and the corrosion resistance is good on both sides, and the vessel is also automatically controlled by the vessel itself It is to provide a cooking container which allows food to be cooked or fried at a temperature to avoid the risk of the container overheating by mistake.

For this purpose, a first subject of the invention is a cooking vessel comprising a bottom and a side wall made of a multilayer material, the multilayer material being continuously from the outside of the container to the inside of the container:

A ferromagnetic alloy layer having a thickness e _E , a Curie temperature of 30 to 350 ° C. and a coefficient of thermal expansion of at least 6.5 · 10 ⁻⁶ K ⁻¹ , the chemical composition being by weight:

32.5% ≤ Ni ≤ 72.5%

5% ≤ Cr ≤ 18%

0.1% ≤ Mn ≤ 0.5%

C ≤ 1%

And optionally one or more elements are selected from Mo, V, Co, Cu, Si, W, Nb, and Al, the total content of these elements being up to 10% and the balance due to iron and smelting Impurity and the chemical composition is:

Cr-1.1Ni + 23.25 ≤ 0%

45Cr + 11Ni ≤ 1360

If Ni ≥ 37.5, Ni + 3Cr ≥ 60%

If Ni ≤ 37.5, Cr ≥ 7.5

More satisfied,

The ferromagnetic alloy layer optionally includes an outer portion inserted between the two austenitic stainless steel layers, and

A core having a thickness e _c and comprising at least one layer selected from aluminum, aluminum alloy and copper, and

A cooking vessel, optionally having a coefficient of thermal expansion of at least 6.5 · 10 ⁻⁶ K ⁻¹ and comprising an inner part, possibly covered with a non-adhesive or anticorrosive coating.

The inventors of the present invention have found that such a container exhibits excellent mechanical, geometrical and dimensional stability, especially after time and may remain flat while the bottom of the container is heated. In a preferred embodiment, the bottom and sidewalls of the container are made of the same multilayer material.

In another preferred embodiment, the multilayer material does not contain any inner parts and e _C / e _E = 6, and more preferably e _C / e _E = 10.

In another preferred embodiment, the inner part is optionally inserted into two austenitic stainless steel layers and consists of a ferritic stainless steel layer having a coefficient of thermal expansion of 9 · 10 ⁻⁶ K ⁻¹ to 14 · 10 ⁻⁶ K ⁻¹ do. This is especially true for the weight percent chemical composition of ferritic stainless steel:

12% ≤ Cr ≤ 25%

C ≤ 0.03%

Si ≤ 0.5%

0.1% ≤ Mn ≤ 0.5%

Al ≤ 0.5%

Ti ≤ 1%

Mo ≤ 2%

V ≤ 2%

Nb ≤ 1%

And the balance is preferably impurities due to iron and smelting.

In another preferred embodiment, the multilayer material of the container is optionally inserted into two layers of austenitic stainless steel and comprises an inner portion consisting of a ferromagnetic alloy layer having a Curie temperature of 30 to 350 ° C., wherein the chemical composition of the ferromagnetic alloy In weight percent:

32.5% ≤ Ni ≤ 72.5%

5% ≤ Cr ≤ 18%

0.1% ≤ Mn ≤ 0.5%

C ≤ 1%

And optionally one or more elements are selected from Mo, V, Co, Cu, Si, W, Nb, and Al, the total content of these elements being up to 10% and the balance due to iron and smelting Impurity and the chemical composition is:

Cr-1.1Ni + 23.25 ≤ 0%

45Cr + 11Ni ≤ 1360

If Ni ≥ 37.5, Ni + 3Cr ≥ 60%

If Ni ≤ 37.5, Cr ≥ 7.5

More satisfied.

The second subject of the invention is an article made of the multilayer material (constituting the cooking vessel) described in the same preferred embodiment as described above.

The invention will be illustrated by the detailed description of three embodiments, given by way of non-limiting example.

The first embodiment relates to a cooking container for cooking or frying food such as rice, fish or meat. The optimum cooking temperature for this kind of food is 220 to 290 ° C. The outer part of the multilayer material to be in contact with the inductor therefore comprises 47 to 55%, preferably 48 to 50% nickel, and 7 to 13%, preferably 7 to 10% chromium and optionally It may be selected to consist of a Fe—Ni—Cr ferromagnetic alloy layer comprising up to 8% cobalt and / or copper. This layer has a Curie temperature of 220 to 290 ° C. and a coefficient of thermal expansion close to 10 · 10 ⁻⁶ K ⁻¹ .

The core of the multilayer material comprises at least one layer selected from aluminum, aluminum alloys and copper. One of the main functions of this core is to distribute heat evenly in the vessel.

For example, this core may consist of three aluminum or aluminum alloy layers. It is desirable to have a thicker and less concentrated center layer in aluminum than the other two layers. Ultra pure aluminum of type AA 3003 or AA 3004 or aluminum alloy can be chosen. The coefficient of thermal expansion of this special triple layer exceeds 22 · 10 ^-6 K ^-1 .

Another example of a core may be a copper layer optionally sandwiched between two aluminum or aluminum alloy layers.

In order to further improve the mechanical and geometrical stability of the vessel, it is possible to add an inner part made of a Fe—Cr—Ti ferritic stainless steel alloy comprising, for example, 16 to 21% chromium and 0.4 to 0.6% titanium; It is also possible to use Fe—Cr—Mo ferritic stainless steel alloys comprising 16 to 21% chromium, 0.6 to 1.5% molybdenum and 0.3 to 0.7% niobium. The Curie temperature of the alloy used exceeds the Curie temperature of the Fe—Ni—Cr alloy in the outer portion and exceeds 400 ° C. The coefficient of thermal expansion is here 10 · 10 ⁻⁶ K ⁻¹ to 14 · 10 ⁻⁶ K ⁻¹ .

Using a layer with a high Curie temperature, such as the inner part of the vessel, generates little heat when the temperature exceeds the Curie point of the outer layer and therefore does not disturb the temperature control of the vessel.

The second embodiment relates to a cooking container for cooking food such as vegetables or fruits. The optimum cooking temperature for this kind of food is 110 to 160 ° C. The outer portion of the multilayer material to be in contact with the inductor may therefore be selected to consist of a ferromagnetic Fe—Ni—Cr alloy comprising 44 to 47% nickel and 12 to 15% chromium. Curie temperature is 140-160 degreeC, and thermal expansion coefficient is close to 9.5 * 10 <^-6> K <^-1> .

The core of the multilayer material comprises at least one layer selected from aluminum, aluminum alloys and copper.

The vessel also contains 19-21% chromium and 0.4-0.6% titanium, the Curie temperature exceeds the Curie temperature of the Fe-Ni-Cr alloy in the outer part and the coefficient of thermal expansion is 11.5 · 10 ^-6 K ^-1 . It includes an inner portion composed of Fe-Cr-Ti ferritic stainless steel alloy.

The third embodiment relates to a cooking container for cooking or warming food such as meat or fish. The optimum cooking temperature for this kind of food is 100 to 260 ° C. The outer part of the multilayer material to be in contact with the inductor therefore comprises 47.5 to 60%, preferably 48 to 50% nickel, and 9 to 15% chromium and optionally up to 8% cobalt and / or copper It may be selected to consist of a ferromagnetic Fe—Ni—Cr alloy layer included together. The Curie temperature of this layer is from 100 to 260 ° C. The coefficient of thermal expansion is 9 · 10 ^-6 K ^-1 to 11 · 10 ^-6 K ^-1 . The thickness e _E of the outer portion is 0.15 to 1.5 mm.

The container does not contain any inner parts, but the core of the multilayer material comprises at least one layer selected from aluminum, aluminum alloy and copper and having a thickness of 1 to 9 mm.

In order to further increase the mechanical and geometrical stability of the container, the thickness of the aluminum core can be further increased.

The vessels described in these three embodiments have a base that remains very stable mechanically and geometrically over time and remains flat during heating, allowing optimization of energy consumption and uniform cooking of food. These containers have good corrosion resistance on both sides. Finally, these three embodiments have the important characteristic of automatically adjusting the temperature of the vessels to a specified value in the application of the embodiments.

Claims (15)

A cooking vessel comprising a bottom and sidewalls made of a multilayer material, The multilayer material is continuously from the outside of the container to the inside of the container: A ferromagnetic alloy layer having a thickness e _E , a Curie temperature of 30 to 350 ° C. and a coefficient of thermal expansion of at least 6.5 · 10 ⁻⁶ K ⁻¹ , the chemical composition being by weight: 32.5% ≤ Ni ≤ 72.5% 5% ≤ Cr ≤ 18% 0.1% ≤ Mn ≤ 0.5% C ≤ 1% Optionally, one or more of the elements is selected from Mo, V, Co, Cu, Si, W, Nb, and Al, the total content of these elements is 10% or less, and the balance is iron and It is an impurity due to smelting and its chemical composition is represented by the following relationship: Cr-1.1Ni + 23.25 ≤ 0% 45Cr + 11Ni ≤ 1360 If Ni ≥ 37.5, Ni + 3Cr ≥ 60% If Ni ≤ 37.5, Cr ≥ 7.5 More satisfactory, the ferromagnetic alloy layer is an outer portion optionally inserted between two austenitic stainless steel layers, and A core having a thickness e _c and comprising at least one layer selected from aluminum, aluminum alloy and copper, and A cooking vessel optionally having a coefficient of thermal expansion of at least 6.5 · 10 ⁻⁶ K ⁻¹ and comprising an inner part possibly covered with a non-adhesive or anticorrosive coating. The method of claim 1, Wherein said multilayer material does not contain any inner portion and has e _c / e _E = 6. The method of claim 1, The multilayer material has a thermal expansion coefficient of 9 · 10 ⁻⁶ K ⁻¹ to 14 · 10 ⁻⁶ K ⁻¹ and includes an inner portion consisting of a ferritic stainless steel layer, optionally inserted between two austenitic stainless steel layers. Cooking container, characterized in that. The method of claim 3, wherein The inner part consists of a layer of ferritic stainless steel, optionally inserted into two layers of austenitic stainless steel, The chemical composition of the ferritic stainless steel is, in weight percent: 12% ≤ Cr ≤ 25% C ≤ 0.03% Si ≤ 0.5% 0.1% ≤ Mn ≤ 0.5% Al ≤ 0.5% Ti ≤ 1% Mo ≤ 2% V ≤ 2% Nb ≤ 1% It is composed of and the balance is impurity due to iron and smelting A cooking container characterized by the above. The method of claim 1 Wherein said multilayer material comprises an inner portion, optionally inserted in two austenitic stainless steel layers, comprised of a ferromagnetic alloy layer having a Curie temperature of 30 to 350 ° C. The method of claim 5, The inner part consists of a ferromagnetic alloy layer, optionally inserted in two austenitic stainless steel layers, The chemical composition of the ferromagnetic alloy is in weight percent: 32.5% ≤ Ni ≤ 72.5% 5% ≤ Cr ≤ 18% 0.1% ≤ Mn ≤ 0.5% C ≤ 1% And optionally one or more elements are selected from Mo, V, Co, Cu, Si, W, Nb, and Al, the total content of these elements being up to 10% and the balance due to iron and smelting Impurity and the chemical composition is: Cr-1.1Ni + 23.25 ≤ 0% 45Cr + 11Ni ≤ 1360 If Ni ≥ 37.5, Ni + 3Cr ≥ 60% If Ni ≤ 37.5, Cr ≥ 7.5 Cooking vessels, characterized in that more satisfied. The method according to claim 3 or 4, The outer portion comprises 47-55% nickel, 7-13% chromium and 0-8% cobalt and / or copper and consists of a ferromagnetic alloy layer having a Curie temperature of 220-290 ° C., said multilayer The material (it) consists of a ferritic stainless steel alloy comprising 16 to 21% chromium and 0.4 to 0.6% titanium, or comprises 16 to 21% chromium, 0.6 to 1.5% molybdenum and 0.3 to 0.7% niobium An inner portion composed of a ferritic stainless steel alloy, the inner portion having a Curie temperature exceeding the Curie temperature of the ferromagnetic alloy of the outer portion, wherein the inner portion has a width of 10 · 10 ⁻⁶ to 14 · 10 ⁻⁶ K ⁻¹ . Having a coefficient of thermal expansion, wherein the core comprises at least one layer selected from aluminum, aluminum alloy and copper A cooking container for cooking or frying food, such as rice, fish or meat, characterized in that. The method according to claim 3 or 4, The outer portion comprises 44 to 47% nickel and 12 to 15% chromium and consists of a ferromagnetic alloy layer having a Curie temperature of 110 to 160 ° C., the multilayer material (it) of 19 to 21% chromium. And an inner portion comprising 0.4 to 0.6% titanium and consisting of a ferritic stainless steel alloy having a Curie temperature above the Curie temperature of the ferromagnetic alloy of the outer portion, the core being a layer selected from aluminum, aluminum alloy and copper To include at least one A cooking container for cooking food, such as vegetables or fruits, characterized in that. The method of claim 2, The outer portion comprises 47,5 to 60% nickel, 9 to 15% chromium and 0 to 8% cobalt and / or copper, has a Curie temperature of 100 to 260 ° C. and a thickness of 0.15 to 1.5 mm consisting of a ferromagnetic alloy layer having e _E , The multilayer material (it) has a thickness of 1 to 9 mm and comprises a core comprising at least one layer selected from aluminum, aluminum alloy and copper. A cooking container for cooking or warming food, such as fish or meat, characterized by the above-mentioned. The method according to any one of claims 1 to 9, And the side wall of the container is made of the same material as the multilayer material at the bottom of the container. A ferromagnetic alloy layer having a Curie temperature of 30 to 350 ° C. and a coefficient of thermal expansion of at least 6.5 · 10 ⁻⁶ K ⁻¹ , the chemical composition being by weight percent: 32.5% ≤ Ni ≤ 72.5% 5% ≤ Cr ≤ 18% 0.1% ≤ Mn ≤ 0.5% C ≤ 1% And optionally one or more elements are selected from Mo, V, Co, Cu, Si, W, Nb, and Al, the total content of these elements being 10% or less, the balance being due to iron and smelting Impurity and the chemical composition is: Cr-1.1Ni + 23.25 ≤ 0% 45Cr + llNi ≤ 1360 If Ni ≥ 37.5, Ni + 3Cr ≥ 60% If Ni ≤ 37.5, Cr ≥ 7.5 More satisfied, The layer optionally comprising a first outer layer inserted into two austenitic stainless steel layers, and A core comprising at least one layer selected from aluminum, aluminum alloy and copper, and Optionally made of a multi-layered material on the opposite side of the first outer layer, having a coefficient of thermal expansion of at least 6.5 · 10 ⁻⁶ K ⁻¹ and comprising a second outer layer possibly coated with a non-adhesive or anticorrosive coating; article. The method of claim 11 Wherein said second outer layer is optionally inserted in two layers of austenitic stainless steel and comprises a ferritic stainless steel layer having a coefficient of thermal expansion of less than 14 · 10 ⁻⁶ K ⁻¹ . The method of claim 12 The second outer layer consists of a ferritic stainless steel layer, optionally inserted in two austenitic stainless steel layers, The chemical composition of the ferritic stainless steel is in weight percent: 12% ≤ Cr ≤ 25% C ≤ 0.03% Si ≤ 0.5% 0.1% ≤ Mn ≤ 0.5% Al ≤ 0.5% Ti ≤ 1% Mo ≤ 2% V ≤ 2% Nb ≤ 1 Wherein the balance is an impurity due to iron and smelting. The method of claim 11 Wherein said multilayer material (it) is optionally inserted in two layers of austenitic stainless steel and comprises a second outer layer having a Curie temperature of 30 to 350 ° C. The method of claim 14, The second outer layer consists of a ferromagnetic alloy layer, optionally embedded in two austenitic stainless steel layers, The chemical composition of the alloy is in weight percent: 32.5% ≤ Ni ≤ 72.5% 5% ≤ Cr ≤ 18% 0.1% ≤ Mn ≤ 0.5% C ≤ 1% And optionally one or more elements are selected from Mo, V, Co, Cu, Si, W, Nb, and Al, the total content of these elements being up to 10% and the balance due to iron and smelting Impurity and the chemical composition is: Cr-1.1Ni + 23.25 ≤ 0% 45Cr + llNi ≤ 1360 If Ni ≥ 37.5, Ni + 3Cr ≥ 60% If Ni ≤ 37.5, Cr≥ 7.5 The article characterized by more satisfying.